The present invention relates to a strip rolling mill and method, and more particularly to a rolling mill having small-diameter work rolls suitable for rolling of hard or extremely thin strips, and a rolling method for use with the rolling mill.
Hitherto, small-diameter work rolls have been employed for rolling of hard or extremely thin strips made of, e.g., stainless steel. As the diameter of work rolls is reduced, bending rigidity becomes smaller correspondingly, which causes a deflection in the horizontal plane, particularly, as a problem. Therefore, cluster type multi-high rolling mills including a Sendzimir mill, and rolling mills equipped with a horizontal deflection preventing mechanism to horizontally support work roll barrels by support rolls, as disclosed in JP, A, 60-18206, have been developed. However, because these rolling mills employ support rolls divided in the axial direction, the divided rolls produce transferred marks on strips, which deteriorate the strip's surface texture. To deal with such a problem, the applicant has previously proposed a rolling mill, as disclosed in JP, A, 5-50109, which prevents deterioration of the strip's surface texture and permits practical use of small-diameter work rolls.
In that rolling mill, multiple rows of support rolls are installed on each of the entry and delivery (back and front) sides so as to support both end portions of a work roll barrel outwardly of the passage of strips having a maximum width, and outermost one of the support rolls is associated with a cylinder for bending the work roll horizontally. A horizontal deflection is prevented by the following three measures; (a) the work roll is set to such an offset position before the start of rolling as that the horizontal force exerted on the work roll will be 0, (b) the offset position of the work roll is also adjusted during the rolling so that the horizontal force is kept at 0, and (c) the horizontal deflection is detected during the rolling and the bending cylinder is controlled so that the detected horizontal deflection is kept at 0. This type of mill will be hereinafter referred to as a UC-1F mill.
JP, A, 61-182807 also discloses a rolling mill provided with measures similar to the above (a) and (b). Further, JP, A, 1-180708 proposes a technique of not only controlling the horizontal deflection of a work roll through an adjustment of the offset position of the work roll and horizontal bending control by a bending cylinder, but also performing the above deflection control in combination with a bending adjustment of the work roll, thereby controlling the shape (flatness) of a strip under rolling. Additionally, JP, A, 63-252608 pertains to a mill using support rolls for supporting each work roll along substantially its entire length, and discloses a method of adjusting the offset position of the work roll so that the horizontal forces are equal to each other vertically and transversely.